Telephone sets, such as portable cellular or cordless telephone sets, are well known in the art. Telephone sets typically include a microphone, an earpiece, a keypad and a loudspeaker. The microphone converts an acoustic input signal into an electric input signal. The earpiece converts an electric output signal into an acoustic output signal. Typically, a person positions the telephone set against the person's head to align the microphone with the person's mouth and to align the earpiece with the person's ear to permit the person to speak the acoustic input signal into the microphone and to listen to the acoustic output signal generated by the earpiece. When a telephone set permits a person to speak and listen to another party at the same time this is known as full duplex voice communications. The keypad permits a person to enter data, such as a phone number, in to the telephone set. The loudspeaker converts an electric output signal into an acoustic output signal. The loudspeaker generates an acoustic output signal at a volume level much higher than volume level of the acoustic output signal generated by the earpiece to permit a person to listen to the acoustic signal generated by the loudspeaker when the telephone set is positioned far away from the person's ear. The volume level of the acoustic output signal from loudspeaker is set at a high enough level so that the person's ear can hear the level of the acoustic output signal generated by the loudspeaker, but not so high as to damage the person's hearing. Use of the loudspeaker is sometimes referred to as a handsfree mode of operation. The handsfree mode may be used when a person holds the telephone set in one hand while entering a phone number into the keypad with the other hand. The handsfree mode may also be used when the person needs to see or touch writable displays while listening to the loudspeaker. The handsfree mode may also be used when several listeners wish to listen to the same conversation over the loudspeaker.
As advances in technology have permitted telephone sets to be made smaller in size and lighter in weight, the available space for implementing necessary features such as microphones and earpieces becomes limited. One such trend in miniaturization is evident when viewing the following U.S. Pat. Nos.: U.S. Pat. No. Des. 369,162--Nagele et al. (single piece housing design), known as a DynaTAC (TM) phone model, U.S. Pat. No. Des. 365,817--Mischenko et al. (main housing with an additional flap housing rotating to cover or uncover a keypad on the main housing), known as a MicroTAC (TM) phone model, and U.S. Pat. No. Des. 369,598--Nagele et al. (clam shell housing design), known as a StarTAC (TM) phone model, all being made and sold by Motorola, Inc. Each of these phone models has an earpiece, a display, a keypad and a microphone carried by one or more housings and arranged on the one housing or on two housings in the order stated here when the two housings are in their opened position during use. The earpiece and the microphone are located at opposite ends of the one or more housings during use to maximize the distance between the earpiece and the microphone and to align the earpiece and the microphone with a person's ear and mouth, respectively, while minimizing the total length of the one or more housings. However, the advantage of having easily accessible features, such as a large keypad or large display, contrasts with the availability of limited space on the one or more housings of the telephone set to place such features.
U.S. Pat. No. 5,721,787 teaches one approach towards miniaturizing a radio device while maintaining a large keypad by placing a loudspeaker behind the keypad. An acoustic output signal generated by the loudspeaker is ported through openings in the keypad into free space outside the radio device. The openings are appropriately aligned and routed to minimize the amount of water intruding through the openings. However, although this configuration provides a place to put a relatively large loudspeaker, the earpiece, the display, the keypad and the microphone carried by the housing are still arranged on the housing in the order stated here. Therefore, the total length of the housing remains unchanged by placing the loudspeaker behind the keypad.
Further, a problem with loudspeakers is that the high volume level of the acoustic output signal may be too loud when the radio device is placed too close to a person's ear. To address this problem, U.S. Pat. No. 5,729,604 teaches a radio device designed so that the loudspeaker will not generate the acoustic signal when the radio device is placed near the person's ear to prevent the person's ear from experiencing a painful acoustic shock by accidentally receiving a high level acoustic output signal from the loudspeaker. In U.S. Pat. No. 5,729,604, the radio device has a proximity sensor to automatically switching between the earpiece and the loudspeaker responsive to the handset being brought into proximity with the person's ear.
Accordingly, there is a need for a telephone set that is shorter, smaller and more integrated while providing the necessary functions of a microphone and an earpiece.